1. Field of the Invention
The present invention relates generally to a suspension system for an automotive vehicle. More specifically, the invention relates to an automotive suspension system which can suppress toe-out change or cause toe-in change in response to shifting of gravity center of the vehicle, which causes vehicular pitching motion.
2. Description of the Prior Art
An independent-type suspension system which constitute background art to the present invention, has been disclosed in the Japanese Utility Model First Publication (Jikkai) Showa 57-141109, published on Sept. 4, 1982. In the shown structure, a wheel spindle assembly rotatably supports a vehicular wheel. The wheel spindle assembly is associated with link mechanism which is connected to a vehicle body. The link mechanism comprises transverse members which extends transversely to the longitudinal axis of the vehicle to determine the transverse position of the wheel spindle assembly. The link mechanism further comprises a longitudinal member extending longitudinally in substantially parallel to the longitudinal axis of the vehicle. Similarly to the aforementioned transverse members, the longitudinal member determines the longitudinal position of the wheel spindle assembly. The transverse and longitudinal members are cooperated with rubber bushings or so forth for elastically or resiliently absorbing vibration to be transmitted from a road wheel to the vehicle body.
The bushings provided in the link mechanism will raise problem of compliance steering. For instance, when vehicle is running in engine braking state to decelerate the vehicle, vehicular gravity center shifts rearwardly to exert rearward force to a wheel axle. At this condition, due to presence of moment of the rearward force, the bushings are deformed to cause compliance steer in toe-out direction. As a result, driving stability of the vehicle tends to be distroied to cause lateral slip at the rear. In order to prevent the vehicular suspension system to fall into unstable driving condition even when the gravity center is shifted rearwardly, the stiffness of the bushings has to be increased. Stiffening the bushing will drop vibration absorbing characteristics. In addition, stiffening the bushing will increase stiffness of the suspension system to increase tendency of giving rough-ride feeling for the driver and/or the passangers riding in the vehicle.